42 Introduction to the Study of Science 



weather conditions. 6. What extreme velocity may be developed in 

 the whirl of a tornado? 7. Explain why buildings often burst out- 

 ward as a tornado passes. 8. What knowledge of the behavior of 

 tornadoes may enable one to avoid them, or find protection from 

 them? 9. Describe a waterspout. 



10. In what regions are thunderstorms common? 11. Describe 

 a thunderstorm. 12. How can a lightning flash be illustrated in the 

 laboratory? 13. What is the normal electrical condition of the air? 

 14. What conditions change the normal electrification? 15. Under 

 what conditions does an electrical discharge take place ? 16. Why does 

 the electrical discharge produce light? Sound? 17. (a) How fast 

 does sound travel? (6) How may this fact be used in determining 

 the distance of a thunderstorm? 18. Why is lightning less frequent 

 in the middle of a storm than at its margins? 19. (a) Why are trees 

 and steeples frequently struck ? (6) What causes the wood to splinter 

 and fly? (c) What are "lightning tubes "? 20. Describe the vari- 

 ous types of electrical discharge. 21. How may lightning rods pro- 

 tect a building? 



VIII. THE MOISTURE OF THE ATMOSPHERE 



25. Relative density of moist' and dry air. The study of 

 cyclonic and anticyclonic areas and of local storms suggests 

 an important question which may be stated thus : Why does 

 warm, moisture-laden air rise when it is met by cold, dry air 

 currents? The answer may be indicated by a simple experi- 

 ment and observations. 



Exercise : Behavior of warm and cold air. Insert a rubber 

 stopper, through which is passed a glass tube six to ten inches long, 

 into a thin glass flask or test tube. Put the end of the tubing into 

 water, and alternately warm and cool the flask. Observe the behavior 

 of the water in the tube. What do you infer as to the change in vol- 

 ume of the air when warmed and when cooled? When does its vol- 

 ume increase and when decrease? What does this show as to the 

 relative weight of equal volumes of warm and of cool air?- When 

 a given volume of warm air meets an equal volume of cold air, which 

 will be forced upward ? 



Study the behavior of warm and cold air in a room heated by a 

 stove or other appliance. What is the temperature of the air near 

 the floor? Of that near the ceiling? Can you detect anything sug- 



